Clamshell lathes are known in the art and can be utilized typically in industrial settings to mill a portion of a generally cylindrical pipe or tube. Non-limiting examples of clamshell lathes are disclosed in U.S. Pat. Nos. 4,739,685; 4,939,964; and 5,549,024. Clamshell lathes in some embodiments are designed as annular devices formed from semi-cylindrical halves connected together around a pipe to be milled. A stationary ring of the clamshell lathe is temporarily fixed to the pipe. A rotatable ring is operatively connected to the stationary ring and is rotatable for example by an air, hydraulic, or electrically-operated motor operatively connected to the rotatable ring. In some embodiments, the motor housing is connected to the stationary ring and has a drive gear that engages gearing located on the rotatable ring. A tool slide can be mounted on the rotatable ring and is adapted to hold a cutting tool for milling the pipe. The tool slide can include a feed mechanism that advances the tool slide and thus the cutting tool preferably in a radial direction toward the pipe in incremental steps upon a predetermined revolution of the ring gear.
Various tripper assemblies are known to the art to actuate the feed mechanism of the clamshell lathe.
U.S. Pat. No. 4,739,685 relates to a lathe having a stationary member and a rotating gear member. A circular race member is connected to the gear member and held in position by means of bearings. Preferably, the bearings have longitudinal axes perpendicular to the top surface of the stationary member. Further, mounting brackets are utilized to reportedly quickly and easily mount a motor onto the stationary member. A two part tool module is also disclosed.
U.S. Pat. No. 5,881,618 relates to a shield slide mechanism for moving the cutting tool of a clamshell lathe. By shielding the mechanism, metal chips created during the cutting process are reportedly precluded from jamming the mechanism and preventing the controlled movement of the cutting tool. The tool block slide assembly incorporates a cam lever actuated feed screw operating through a unidirectional roller clutch rather than a conventional starwheel.
WO 2008/052106 relates to a tripper assembly described for use with a clamshell lathe having a stationary ring and a rotatable ring including a tool module for holding a tool bit. The tool module has a starwheel with a plurality of teeth coupled to a feed screw for moving a tool bit in a radial direction with respect to the rings as the starwheel rotates. The tripper assembly includes a bracket affixed to the stationary ring of the lathe, a radially extending shaft mounted in the bracket, a pin holder mounted on the shaft, and a radially extending pin held by the pin holder. Rotation of the shaft moves the pin along an arc to move the pin between an engaged position and a disengaged position with respect to the starwheel. When the pin is at the engaged position, upon each revolution of the starwheel, the pin engages a tooth on the starwheel to rotate the starwheel.